It is common practice in the analysis of light absorbing fluids to immerse in the fluid one end of a probe having an opening therein through which the fluid may flow, transmit light from a source across the opening onto a reflector which reflects the light back across the opening, collect the reflected light, and conduct it to one or more devices for analysis.
There are many occasions in which it would be desirable to adjust the length of the path across the opening. For example, the translucency of one fluid may be sufficient to enable light to traverse a relatively short path, but insufficient to enable the light to traverse a longer path. By adjusting the length of the light path variations in translucency can be accommodated.
Heretofore, adjustment of the length of the light path has been accomplished by removing one mirror support and substituting therefor another mirror support which, when installed in the probe, provides a different path length to be traversed by the illuminating light and the reflected light. This kind of adjustment is troublesome and time consuming inasmuch as it necessitates physical replacement of one mirror support with another.
Light transmitted by conventional probes often is introduced into the fluid medium in such manner that the light is refracted in its passages through the fluid, thereby making it difficult, if not impossible, to analyze simultaneously light of different wave lengths.
Conventional probes of the general class to which the invention relates utilize reflectors exposed to the fluid with which they are used, thereby subjecting the reflective surfaces thereof to damage, either as a result of handling or from contact with the fluid in which the probe is immersed.
Apparatus constructed in accordance with the invention overcomes the objectionable characteristics referred to above of known probes for the in situ analysis of light absorbing fluids.